You can use fine grit sand paper to smooth out the "pits" & then use valve grinding paste to smooth it even further.
I basically pasted a bit of valve grinding paste on the slide pin and kept sliding it in and out for five minutes or so.
It came out good, but make sure to properly clean the slide hole & pin to remove all the grinding paste.
You won't find the pins by themselves, but the minor caliper repair kit is around $30.
Even though I did it, it's not worth it IMO, 'cos I got a used caliper after spending that $30 and time on mine 'cos the piston bore
of the caliper was also pitted from rubber boot failure and dust getting into it.
I bought a used caliper for the same price with everything in good condition.
If your one's rubber boots are in good nick, then you can simply avoid the rebuild kit and do the smoothing of the slide pin as above.
Sand paper, grinding paste & rubber grease only cost few peanuts. Rubber grease comes in small sachets at SuperCheap auto.
There's an even better grease for the job that was pointed out to me by a member here while ago. I think it's "copper grease" or something.
I would rebuild it without a rebuild kit, 'cos rubber boots are in good nick in yours. It's a fairly easy job in your case.
P.S. I reckon you can even fit the slide pin to a drill with a chuck big enough and smooth the bore/hole & pin in less than a minute.